Hey Ed, I smoked a 10 lbs whole turkey and used 3oz of wood chips and it was too much smoke, kind of ruined the final product. Everyone's taste is different, but I would go with 1.5 - 2 oz at the most for your breast. I believe there was a recent post and it was definitely less than 2 oz that was used for a whole bird.
Since turkey or chicken does not have a lot of flavour, I find that they tend to really pick up the smoke flavour with very little wood. I included the path below for the post, sorry I couldn't copy the link.
All Things Smoked! » Model #1 » The Little Guy!! » Lil Butterball